Fig. 3
From: Ultrahigh-pressure acoustic wave velocities of SiO2-Al2O3 glasses up to 200 GPa
In situ high-pressure Brillouin spectra. Spectra of a SA1 at 20 GPa, b SA2 at 16 GPa, c SA1 at 169 GPa, and d SA2 at 189 GPa. TA and LA indicate transverse and longitudinal acoustic modes of the Brillouin shift, respectively. Ghost peaks are artifacts of the interferometry method. LA peaks are masked above around 45 GPa because of the overlap of the diamond’s TA peaks